1. Field of the Invention
The present invention relates to an automatic seepage meter for measuring groundwater-surface water exchange in a mixed zone of stream.
2. Description of the Related Art
Seepage meters are instruments for measuring the flow of water between groundwater and a surface water body such as a lake, wetland, estuary, or stream. Such seepage meters were used in the 1940s and 1950s to measure water loss in irrigation canals (Israelson and Reeve, 1944; Warnick, 1951; Robinson and Rhower, 1952), and Lee (1977) devised and used a seepage meter of half-barrel shape to evaluate an interaction between groundwater and surface water.
The seepage meter initially proposed by Lee (1977), as illustrated in FIG. 1, includes a drum 100 which one side is closed. The drum 100 is buried into streambed sediment and connected to a collection bag 103 by a hose to measure seepage flux (discharge of groundwater to surface water or recharge of groundwater by surface water). That is, after filling the collection bag 103 by a certain amount of water before measuring seepage flux and elapsing a certain time, an increased or decreased amount of water in the collection bag 103 is measured. An amount of water in the collection bag 103 is increased in a gaining stream where groundwater discharges into stream, and decreased in a losing stream where groundwater is recharged by surface water.
Since the seepage meter proposed by Lee (1977) is a manual measuring type that directly measures an amount of water increased or decreased in the collection bag 103 after elapsing a certain time, it is difficult to obtain information on the temporal evolution of seepage.